U.S. Geological Survey2007BATHY - Bathymetry within the inner shelf of Long Bay, South Carolina collected by the USGS, 1999-2003 (Grid)1.0raster digital dataOpen-File Report2005-1346Woods Hole Science Center, Woods Hole, MAU.S. Geological Survey, Coastal and Marine Geology Programhttp://pubs.usgs.gov/of/2005/1346/arcgis/bathy/bathy_grd.zipBaldwin, W.E.Denny, J.F.Schwab, W.C.Gayes, P.T.Morton, R.A.Driscoll, N.W.2007Geologic Framework Studies of South Carolina's Long Bay from Little River Inlet to Winyah Bay, 1999-2003; geospatial data release1.0Open-File Report2005-1346Woods Hole Science Center, Woods Hole, MAU.S. Geological Survey, Coastal and Marine Geology Programhttp://pubs.usgs.gov/of/2005/1346/In 1999, the USGS, in partnership with the South Carolina Sea Grant Consortium, began a study to investigate processes affecting shoreline change along the northern coast of South Carolina, focusing on the Grand Strand region. Previous work along the U.S. Atlantic coast shows that the structure and composition of older geologic strata located seaward of the coast heavily influences the coastal behavior of areas with limited sediment supply, such as the Grand Strand. By defining this geologic framework and identifying the transport pathways and sinks of sediment, geoscientists are developing conceptual models of the present-day physical processes shaping the South Carolina coast. The primary objectives of this research effort are: 1) to provide a regional synthesis of the shallow geologic framework underlying the coastal upland, shoreface and inner continental shelf, and define its role in coastal evolution and modern beach behavior; 2) to identify and model the physical processes affecting coastal ocean circulation and sediment transport, and to define their role in shaping the modern shoreline; and 3) to identify sediment sources and transport pathways; leading to construction of a regional sediment budget.This data set contains swath bathymetric data collected between 1999 and 2003. These data are used to define the sea-floor morphology offshore of the Grand Strand, South Carolina.19991029, 20000313, 20010501, 20020502, 20020603, 2003050119991112, 20000330, 20010515, 20020508, 20020618, 20030521ground conditionCompleteNone planned-79.177101-78.50283233.87665433.144166GeneralU.S. Geological SurveyUSGSWoods Hole Science CenterWHSCCoastal and Marine Geology ProgramCMGPbathymetryswath bathymetryinterferometrysea-floor morphologyArcRaster gridWHSC field activity serial number 00014WHSC field activity serial number 01008WHSC field activity serial number 02011WHSC field activity serial number 02014WHSC field activity serial number 03009WHSC field activity serial number 99044ISO 19115 Topic Categoryoceansoceans and coastaloceans and estuarieselevationGeneralSouth CarolinaGrand StrandNorth Myrtle BeachMyrtle BeachSurfsideGarden CityPawleys IslandWaites IslandSoutheast United StatesUnited StatesAtlantic OceanNoneThese data are NOT to be used for navigation. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.U.S. Geological SurveyJane DennyGeologistmailing and physical address384 Woods Hole RoadWoods HoleMA02543-1598USA508-548-8700 x2311508-457-2310jdenny@usgs.govhttp://pubs.usgs.gov/of/2005/1346/images/bathy_grd.jpgcolor coded image of bathymetryJPEGMicrosoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.1.0.780These data are internally consistent and have been compared to multibeam and single-beam bathymetric surveys to check for accuracy. Any differences between this bathymetric data set and others were determined to be within acceptable error given the inherent differences in the various bathymetric data sets (i.e. acquisition system, mode of navigation, density of point, and or swath bathymetry).These data were checked for consistency by plotting the point data with the contoured surface and eliminating spurious and anomalous soundings. All data were acquired with an SEA, ltd SwathPlus interferometric sonar (234 kHz).CompleteDGPS is assumed to be accurate within 1-2 meters. Standard GPS is assumed accurate within 5-10 meters. 99% of the positional data is DGPS. Unless noted, all GPS/DGPS data is referenced to WGS84 (NAD83). The configuration of the fathometer is as follows: The fathometer is mounted on either the port or starboard side of the vessel. Offset between the sidemount and GPS antennae is measured. No measurements were taken of ship's pitch, yaw, heave, or change in draft due to water and fuel usage. Motion of the fathometer is not measured. Horizontal accuracy of the fathometer is assumed to be within 3 meters.Ship motion was recorded with a TSS DMS 2-05 Attitude Sensor, mounted directly above the SEA SwathPlus transducers. Navigation was recorded using a Differential Global Positioning System (DGPS). The interferometric sonar is an angle-measuring system; depth accuracy decreases with increasing horizontal range. The combined angular accuracy of the SwathPlus system and the TSS DMS 2-05 attitude sensor is documented as 0.1 degrees. Assuming a constant angular accuracy, and using the International Hydrographic Standard (IHO) of a required 0.3 meter accuracy in < 30 meter water depth, all data collected within the survey fall within the IHO accuracy standards. However, vertical accuracy is also directly affected by the accuracy of both the navigation system and tidal measurements.
Bathymetric data were corrected for variations in the speed of sound throughout the water column; sound velocity profiles were acquired throughout the survey area using an Applied MicroSystems SVPlus Sound Velocimeter. These data were downloaded and reformatted to the required format needed for use within University of New Brunswick's Ocean Mapping Group (OMG) SwathEd multibeam processing software. The raw Submetrix 2000 Series data were "unraveled" and reformatted into the OMG format. This process creates several files on disk:
1) bathymetric soundings
2) raw sidescan-sonar backscatter
3) navigation
4) parameter files describing the configuration of the system
(i.e. offsets between motion reference unit and GPS antenna, etc).
This process also incorporates the sound velocity profiles in order to properly trace the rays given the structure of the water column.
2004Jane DennyU.S. Geological SurveyGeologistmailing and physical address384 Woods Hole RoadWoods HoleMA02543-1598USA508-548-8700 x2311508-457-2310jdenny@usgs.govThe OMG formatted bathymetric data were then graphically edited using the SwathEd multibeam processing software. This enabled editing on a "ping-by-ping" basis, both in the across- and along-track dimension. Spurious or erroneous data were removed. The navigation data were also graphically examined for each line of data.2004Jane DennyU.S. Geological SurveyGeologistmailing and physical address384 Woods Hole RoadWoods HoleMA02543USA508-548-8700 x2311508-457-2310jdenny@usgs.gov
Navigation data output during the unravel were reformatted for entry into MATLAB. The time of day and position were used to extract the tidal elevation from within the ADCIRC circulation model. The ADCIRC circulation model is referenced to Mean Sea Level. Verified tidal data from the NOAA tidal gauge at SpringMaid Pier, SC were downloaded, referenced to Mean Lower Low Water (MLLW). A low-pass filter was applied to the NOAA tide data; the residual was assumed to represent the wind component of sea surface elevations. Tidal elevation (output from ADCIRC) and wind component (NOAA tide station) represent total variation in surface elevations. These data were then written to an ASCII file and reformatted to OMG format for use within SwathEd. The tidal data were then written into the headers of the OMG formatted files, using the 'mergedTide' command.
(SwathEd Commands:
binTide -year XXX adcirc_wind.txt tide.bin
mergeTide -tide tide.bin *.merged
)
SwathEd Software was used to grid the bathymetric data at 20 m grid cell size utilizing the 'weigh_grid' command.
weigh_grid -omg -butter -power 2 -cutoff 10 -lambda 2.5 Grid *.merged
The gridded data were then viewed using the SwathEd Jview Command. The PatchTool was used to assess the roll misalignment of the data; slight roll misalignment artifacts were visible in the gridded data. The PatchTool is a QC tool to assess the degree to which the head (transducers and MRU) needs to be 'rolled' to achieve the proper alignment. QC was also preformed on the navigation. Edits were made as necessary. After the needed adjustments were recorded, the configuration and navigation were remerged with the OMG bathymetric data using the mergeNav and mergeAtt commands.
mergeNav -use_params 0 -nav *.nav -swath *.merged)
The remerged data were regridded for a second round of QC. The roll misalignment artifacts were no longer visible in the gridded data.
The bathymetric data to this point have been edited, navigation, edited, tidal elevations relative to MLLW incorporated in the data, sound velocity corrections applied, and roll misalignment rectified. Next the data need to be interpolated to generate a continuous bathymetric surface.
The SwathEd 'make_blank' command was used to generate a 20 meter grid for the survey area. The OMG formatted bathymetric files were then written into the 20 meter grid using the 'weigh_grid' command.
Due to noise within the far range of the sonar signal, the 'max_incidence' parameter was used. This essentially limits the across track data range of the data; thus elimination noise.
(weigh_grid -omg -butter -power 2 -cutoff 20 -lambda 10 -max_incidence 60 Grid *.merged)
The 20 meter gridded data were then exported to an xyz ASCII file.
(r4toASCII -utm -merid -81 20m_grd 20m.xyz)
2004Jane DennyU.S. Geological SurveyGeologistmailing and physical address384 Woods Hole RoadWoods HoleMA02543-1598USA508-548-8700 x2311508-457-2310jdenny@usgs.gov
The 20m xyz ASCII data were then imported into Geographic Resources Analysis Support System (GRASS). A spline with tension and directionality interpolation routine was used in order to generate a continuous bathymetric surface from the interferometric sonar data. After many iterations, the gridding parameters resulting in a gridded dataset with the least amount of visible artifacts were as follows:
s.surf.rst input=20m.xyz elev=grid100m field=1 tension=200 dmin=20 theta=45 scalex=0.5 smooth=2
A smoothing filter (comparable to a median/mean filter) was applied to the dataset.
2004Jane DennyU.S. Geological SurveyGeologistmailing and physical address384 Woods Hole RoadWoods HoleMA02543-1598USA508-548-8700 x2311508-457-2310jdenny@usgs.gov
The final grid was then exported as an ESRI Binary Grid.
r.out.arc in=grid100m out=grid100m.asc
The exported data were then imported to ArcGIS 9.0 using the ASCIItoGRID command. The projection was then defined: UTM, zone 17 projection, WGS84 Ellipsoid.
2004Jane DennyU.S. Geological SurveyGeologistmailing and physical address384 Woods Hole RoadWoods HoleMA02543-1598USA508-548-8700 x2311508-457-2310jdenny@usgs.govRasterGrid Cell8006101Universal Transverse Mercator170.999600-81.0000000.000000500000.0000000.000000row and column100.000000100.000000metersD_WGS_1984WGS_19846378137.000000298.257224Mean lower low water1metersExplicit depth coordinate included with horizontal coordinatesU.S. Geological Surveymailing and physical address384 Woods Hole RoadWoods HoleMA02543-1598USA508-548-8700508-457-2310Downloadable DataAlthough all data have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.ESRI GridArcGIS 9.0ESRI Grid FileGrid containing swath bathymetric data collected offshore of the Grand Strand, SCno compression applied3.261http://pubs.usgs.gov/of/2005/1346/arcgis/bathy/bathy_grd.zipData can be downloaded via the World Wide Web (WWW)DVD-ROM4.75GbytesUDFnoneThese data are available in Environmental Systems Research Institute (ESRI) Raster GRID format. The user must have software capable of importing and processing the data file.20070123Jane DennyU.S. Geological SurveyGeologistmailing and physical address384 Woods Hole RoadWoods HoleMA02543-1598USA508-548-8700 x2311508-457-2310FGDC Content Standards for Digital Geospatial MetadataFGDC-STD-001-1998local timeNoneNonehttp://www.esri.com/metadata/esriprof80.htmlESRI Metadata Profile